Fluorescent lamps are generally well known to provide illumination and lighting. A glass tube or envelope is coated or covered on its interior surface with a fluorescent powder typically a phosphor coating using sputtering, vapor deposition or other well known techniques. The tube is filled with an inert gas such as argon or a mixture of argon and neon, and a minute droplet of low pressure mercury vapor. A cap holding an electrode which extends into the glass tube is used to seal each end of the lamp. When the lamp is switched on, a current passes through the electrodes causing them to heat up and emit electrons that electrically charge or ionize the gas within the tube. The ionized gas becomes a conductor allowing increased current, essentially arcing, to jump from one electrode to the other electrode resulting in the emission of ultraviolet radiation. The ultraviolet radiation is then absorbed by the phosphor coating on the inner surface of the tube converting it into visible light. Although fluorescent lamps are in wide spread use in commercial and industrial applications and for lighting systems, there are a number of limitations and drawbacks associated with fluorescent lighting. Typically, the fluorescent tube is limited in the number of different sizes due to the requirement that the lamp must be mounted in a fixture to hold the tube and because the tube must be sealed during manufacture it is impractical to provide many different lengths without custom manufacturer to a given application. Additionally, fluorescent tubes are fragile and unless extreme care is taken in handling the tubes the fluorescent lamp is subject to breakage and possible injury to a user. A further disadvantage of fluorescent lamps is that a high voltage is necessary to start the lamp to initially ionize the inert gas to create the required ultraviolet radiation. Fluorescent lamps are also inefficient with respect to the light produced in that light is directed 360 degrees around the tube and therefore only a portion of the light is directed downward to a work surface or to illuminate a given area. The light that is emitted upward must be reflected through use of reflectors to redirect the light downward to the work surface or area to be illuminated otherwise the light that is generated in the generally upward direction is lost relative to its illumination capability of a work surface or area.
Electroluminescent (EL) lamps and lighting systems such as described in U.S. Pat. Nos. 5,019,748 and 6,833,669, assigned to the assignee as the present invention are known to provide large scale flexible lighting panels that are flexible and not restricted in size at the time of manufacture so that a user may make the panel in a desired size and shape for a particular lighting application without restrictions on the initial manufacturing process. Such EL lamps are manufacturable using roll-to-roll and web-to-web processing currently in widths up to 54 inches and lengths of 2,400 feet. The disclosures of U.S. Pat. Nos. 5,019,748 and 6,833,669 are incorporated herein by reference. The advantage with such EL lamps is that 100 percent of the visible light generated is directed downward toward the work surface or the area to be illuminated and thus increased efficiency over fluorescent lamps. In addition, EL panel lamps such as described above are robust and easily handled by a user without danger of breakage and are flexible so that the EL panel lamps may be bent around corners or conformed to contoured surfaces as required. Although such EL lamps provide benefits over fluorescent lamps, they are relatively expensive in comparison to conventional fluorescent lamps.
Although EL lamps provide a flat flexible lamp, they are not entirely satisfactory for general lighting applications which typically require much higher or brighter intensity than that producable by such electroluminescent lamps. Additionally, the life of such lamps is limited and more expensive to produce because EL phosphor is more expensive than fluorescent phosphor such as used in fluorescent lamp tubes.
Accordingly, it would be desirable to combine the benefits of fluorescent lamps and electroluminescent lamps to provide a flat, flexible fluorescent lamp to provide benefits not available in either EL lamps or in fluorescent lamps.
It is an object therefore of the present invention to provide flexible fluorescent lamp that has a brighter intensity, longer life, lower cost to manufacture and a lower operating cost.
It is a further object of the present invention to provide a self-luminous base lamp material for construction of a flat flexible fluorescent lamp.